The transmission of the atmosphere along a path is defined as the amount of light that is not lost due to molecular scattering and/or absorption or newly created by emitting sources within the path. The transmission of the atmosphere is dependent on observation wavelength and path length, along with the molecular, aerosol, and particulate composition. A transmissometer is an instrument used to measure transmission of the atmosphere at a particular wavelength over a path. A transmissometer is particularly useful for characterizing propagation paths for laser systems. The transmission of the atmosphere effects how much light will actually reach the intended target. This metric is important in designing free-space optical and infrared systems such as laser radar, laser communications, laser range finders, etc. Transmissometers can also be used to measure molecular scattering in gas samples and attenuation in material samples.
Current transmissometer designs can be physically bulky, electronically complex, and susceptible to noise interference which limits dynamic range. A transmissometer design that reduces complexity and size, weight, and power (SWAP), improves noise resiliency, and increases signal-to-noise (SNR) ratio and dynamic range is highly desirable.